The present invention relates generally to the field of wireless communication, and more particularly to data transmission.
In recent years, the demand for speeding up the wireless communication is increasing to achieve real-time transmission and reception of rich content, such as moving images, and to achieve seamless connection with wired communication. To achieve such high-speed, high-capacity data communication, there are expectations for a millimeter-wave wireless communication technique that can achieve high-speed wireless communication at a data rate greater than Gbps.
A wireless communication apparatus typically includes a digital processing unit (baseband) that exclusively handles digital signal processing and an analog processing unit (RF: Radio Frequency) that exclusively handles analog signal processing. The circuit blocks are typically connected to each other through an alternating current (AC) coupling (capacitive coupling) to absorb a difference in input-output bias voltage and to achieve stable operation.
A direct current (DC) balance is necessary in the AC coupling, and accurate data transmission is difficult if many DC components or low-frequency components are included. Since a deviation of bits in a transmission signal generates DC offset components, preprocessing is typically applied by a scrambler or a data encoding technique to sufficiently diffuse transmission bits to avoid the deviation. Examples of the data encoding include a) 8b/10b encoding, b) bit stuffing as seen in, for example, S. Aviran, et. al, “An Improvement to the Bit Stuffing Algorithm”, IEEE Trans. Inform. Theory, Vol. 51, pp 2885-2891, 2004, and c) Fibonacci coding, as seen in, for example, A. S. Fraenkel, et. al, “Robust Universal Complete Codes for Transmission and Compression”, Discrete Applied Mathematics, vol. 64, pp 31-55, 1996.
However, additional bits are inserted in the data encoding technique, and in return, the encoding efficiency is reduced. Meanwhile, with just the scrambler, the bits are apparently uniformly dispersed, but a deviation may be generated as a result of the scrambling. More specifically, the scrambler may continuously generate the same bits in a short term, and stochastically, there is a bit deviation. A DC imbalance occurs in the short term, and this worsens the error rate.
If the signal is handled as a binary digital signal, the DC offset components may not be a problem. However, a modulation system, such as 16 Quadrature Amplitude Modulation (QAM), for modulating the amplitude is adopted in a high-speed communication technique, such as millimeter-wave communication, to further speed up the data rate, and the DC offset components have a non-negligible effect on multi-level determination in the amplitude direction. Furthermore, when signal determination boundaries are finer as in 64 QAM and the like, the effect of the DC offset components becomes greater.